Mesh routing of sleepy sensor data

ABSTRACT

HVAC components having improved efficiency are described. In one embodiment, excessive sleep current draw in a battery-powered device having a microcontroller is detected by measuring a voltage drop across a MOSFET device coupled in a forward-conducting orientation in series between the battery and the microcontroller, causing a transistor to conduct when the voltage drop exceeds a predetermined threshold to generate a first trigger signal, integrating the first trigger signal to generate a second trigger signal, and generating an interrupt to the microcontroller. In another embodiment, a battery-saving method of operating an HVAC component includes maintaining the HVAC device in the sleep mode, receiving a user input to wake the device, transmitting a data request and returning the HVAC component to the sleep mode, waking up the HVAC device to poll an adjacent network node storing a cached response, displaying the response, and returning the HVAC device to sleep.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Utility patent applicationSer. No. 16/786,596, to issue as U.S. Pat. No. 11,172,446, entitled“MESH ROUTING OF SLEEPY SENSOR DATA” and filed Feb. 10, 2020, which is acontinuation of U.S. Utility patent application Ser. No. 15/542,320, nowU.S. Pat. No. 10,560,894, entitled “MESH ROUTING OF SLEEPY SENSOR DATA”and filed Jul. 7, 2017, which is a U.S. National Phase Application filedunder 35 U.S.C. § 371 that claims the benefit of and priority toInternational Application PCT/US16/13234 entitled “IMPROVED WIRELESSHVAC COMPONENTS” and filed Jan. 13, 2016, which claims the benefit ofand priority to U.S. Provisional Application Ser. No. 62/102,968entitled “IMPROVED WIRELESS HVAC COMPONENTS” and filed Jan. 13, 2015,and U.S. Provisional Application Ser. No. 62/107,074 entitled “IMPROVEDWIRELESS HVAC COMPONENTS” and filed Jan. 23, 2015, the entirety of eachof which is hereby incorporated by reference herein for all purposes.

BACKGROUND 1. Technical Field

The present disclosure is directed to systems, apparatus, and methodsfor improving wireless HVAC components, and in particular, HVAC sensorsand HVAC controllers having reduced power consumption, lowermanufacturing costs, and increased reliability.

2. BACKGROUND OF RELATED ART

Heating, ventilation, and air conditioning systems (HVAC systems)typically utilize one or more sensors, thermostats, and/or HVACcontrollers to monitor environmental conditions in a building and tooperate HVAC equipment installed at the building. Prior art systemsutilize components which are interconnected using traditionalhard-wiring techniques using electrical conductors routed within thephysical structure. Hard-wired systems are generally reliable, but thecosts of cabling and installation are high. This is particularly truewhen installing devices in existing structures where cabling must besnaked through walls and ceilings. More recently, the use of wirelessHVAC devices has become popular since installation is simple andlow-cost. Existing wireless devices may have drawbacks in that thebatteries used in these devices have a limited lifespan and requireperiodic maintenance and replacement to ensure the HVAC system continuesto function reliably. Depending on various system requirements, suchwireless sensors, HVAC controllers, and other wireless devices may berequired to include, or not include, a user-visible panel or userinterface. The need to design, test, and manufacture different versionsof wireless devices increases costs and reduces profits and marketadvantage. A wireless HVAC device which offers reduced powerconsumption, lower manufacturing costs, and increased reliability wouldbe a welcome advance in the art.

SUMMARY

In one aspect, the present disclosure is directed to a method of sensingexcessive sleep current draw in a battery-powered device having amicrocontroller. In an embodiment, the disclosed method includesmeasuring a voltage drop across a MOSFET device coupled in aforward-conducting orientation in series between the battery and themicrocontroller; causing a transistor to conduct when the voltage dropexceeds a predetermined threshold to generate a first trigger signal;integrating the first trigger signal to generate a second triggersignal; and generating an interrupt to the microcontroller in responseto the second trigger signal. In an embodiment, the predeterminedthreshold is consistent with excessive current draw during sleep. In anembodiment, the method includes transmitting, from the microcontroller,a fault signal in response to the interrupt.

In another aspect, the present disclosure is directed to a sleep currentfault detection circuit for use with a powered device operable in asleep mode and an awake mode. In an embodiment, the circuit includes aMOSFET, the drain terminal thereof coupled to a current source, the gateterminal thereof coupled to a powered device, the source terminalthereof coupled to ground; a first transistor, the emitter terminalthereof coupled to the drain terminal of the MOSFET and configured toconduct when the voltage across the drain terminal of the MOSFET and thesource terminal of the MOSFET exceeds a predetermined voltage; a secondtransistor, the base terminal thereof coupled to the collector of thefirst transistor, the collector terminal thereof coupled to an R-Cfilter; and a third transistor, the base terminal thereof coupled to theR-C filter, the collector terminal thereof coupled to an interruptterminal of the powered device. In an embodiment, the gate terminal ofthe MOSFET may be coupled to an output of the powered device. In anembodiment, the output of the powered device turns off the MOSFET priorto entering sleep mode. In an embodiment, the output of the powereddevice turns on the MOSFET when entering awake mode. In an embodiment,predetermined voltage may be about 0.5 volts.

In yet another aspect, the present disclosure is directed to anenergy-efficient method of transmitting data from the end node to adestination node in a mesh network having an end node operable in asleep mode and an awake mode. The method includes transmitting a firstmessage, the first message including a tag ID of the destination nodeand message data, from the end node to a parent node of the end node;receiving, at the end node, a first acknowledgement from the parent nodeacknowledging receipt of the first message by the parent node; causingthe end node to enter sleep mode in response to the acknowledgement;determining, at the parent node, whether the parent node is thedestination node; and transmitting a second message, the second messageincluding the destination node tag, the message data, and a networkaddress of the parent node, to the destination node in response todetermination that the parent node is not the destination node.

In an embodiment, the method includes storing, at the parent node, arelationship between the tag ID of the end node and a network address ofthe node from which the intervening node received the second message. Inan embodiment, transmitting a second message including data from thefirst message from the parent node to the destination node includesrelaying the second message through an intervening node. In anembodiment, the method includes storing, at the intervening node, arelationship between the tag ID of the end node and a network address ofthe node from which the intervening node received the second message. Inan embodiment, the method includes receiving, at the parent node, asecond acknowledgement from the destination node; caching the secondacknowledgement at the parent node; receiving, from the end node, a pollrequest; and transmitting the second acknowledgement to the end node inresponse to the poll request. In an embodiment, the firstacknowledgement includes a data link layer acknowledgement. In anembodiment, the second acknowledgement includes an application layeracknowledgement.

In still another embodiment, the present disclosure is directed to amethod of extending battery life in a wireless HVAC component operablein a sleep mode having a first power consumption and in an awake modehaving a greater power consumption than when the component is in thefirst mode. In an embodiment, the method includes operating the HVACcomponent in the sleep mode; receiving, at a user interface element ofthe HVAC component, a user input; operating the HVAC component in theawake mode; transmitting, from the HVAC component, a data requestmessage, wherein the data request message includes a device identifierof the destination device from which the data is requested; returningthe HVAC component to the sleep mode; forwarding the data requestmessage to the destination device; transmitting, from the destinationdevice, a response to the data request message; returning the HVACcomponent to the awake mode; polling an adjacent network node by theHVAC component; receiving, at the HVAC component, the response to thedata request message; displaying, on the HVAC component, informationderived from the response and; returning the HVAC component to the sleepmode. In an embodiment, the method includes caching, at an adjacentnetwork node, the response to the data request message. In anembodiment, the user interface element may include a pushbutton and aproximity sensor. In an embodiment, the forwarding includes relaying thedata request message through one or more intervening devices. In anembodiment, the data request message may include a set point, a modeindicator, a temperature indicator, an HVAC system status, a fuelindicator, an energy indicator, a battery level indicator, and a signalstrength indicator. In an embodiment, the mode indicator may include acooling mode indicator, a heating mode indicator, a fan mode indicator,a ventilation mode indicator, and a service mode indicator. In anembodiment, the temperature indicator may include an indoor temperature,an outdoor temperature, a refrigerant temperature, an HVAC equipmentinlet temperature, and an HVAC equipment outlet temperature. In anembodiment, the fuel indicator may include a fuel flow rate indicator, afuel level indicator, and a fuel pressure indicator. In an embodiment,the energy indicator may include a voltage indicator, a currentindicator, and an alternating current frequency indicator, a utilityenergy source indicator and a backup energy source indicator.

In a further embodiment, the present disclosure is directed to a kit formanufacturing an HVAC sensor assemblable in a first configuration havingan exposed display and second configuration having a hidden display. Inan embodiment, the kit includes a printed circuit board having a displayside and a non-display side, the display side including a display moduledisposed thereon; a first housing assembly having a user surface and amounting surface; the user surface having a display opening definedtherein; the first housing assembly configured to operatively receivethe printed circuit board whereby the display module faces the usersurface and is visible through the display opening; and a second housingassembly having a user surface and a mounting surface and configured tooperatively receive the printed circuit board whereby the display modulefaces an interior surface of the housing. In an embodiment, the printedcircuit board includes a switch assembly disposed on the display sidethereof; the first housing assembly further comprises a switch assemblyopening defined in the user surface thereof, the switch assembly openingconfigured to operably receive the switch assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the disclosed system and method are describedherein with reference to the drawings wherein:

FIG. 1 is a block diagram of an embodiment of an improved wireless HVACdevice in accordance with the present disclosure;

FIG. 2 is a schematic diagram of an embodiment of a sleep current faultdetection circuit in accordance with the present disclosure;

FIGS. 3A-3F are diagrams illustrating a prior art mesh network;

FIGS. 4A-4F are diagrams illustrating aspects of an energy-efficientmesh network in accordance with an embodiment of the present disclosure;

FIGS. 5A-5D present embodiments of a wireless HVAC device having areversible printed circuit board and assemblable in a firstconfiguration having an exposed display and second configuration havinga hidden display; and

FIGS. 6 and 7 illustrate a method of extending battery life in awireless HVAC device in accordance with an embodiment of the presentdisclosure.

The various aspects of the present disclosure mentioned above aredescribed in further detail with reference to the aforementioned figuresand the following detailed description of exemplary embodiments.

DETAILED DESCRIPTION

Particular illustrative embodiments of the present disclosure aredescribed hereinbelow with reference to the accompanying drawings;however, the disclosed embodiments are merely examples of thedisclosure, which may be embodied in various forms. Well-known functionsor constructions and repetitive matter are not described in detail toavoid obscuring the present disclosure in unnecessary or redundantdetail. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present disclosure in virtually anyappropriately detailed structure. In this description, as well as in thedrawings, like-referenced numbers represent elements which may performthe same, similar, or equivalent functions. The word “exemplary” is usedherein to mean “serving as an example, instance, or illustration.” Anyembodiment described herein as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other embodiments. The word“example” may be used interchangeably with the term “exemplary.”

The present disclosure is described herein in terms of functional blockcomponents and various processing steps. It should be appreciated thatsuch functional blocks may be realized by any number of hardware and/orsoftware components configured to perform the specified functions. Forexample, the present disclosure may employ various integrated circuitcomponents, e.g., memory elements, processing elements, logic elements,look-up tables, and the like, which may carry out a variety of functionsunder the control of one or more microprocessors or other controldevices.

Similarly, the software elements of the present disclosure may beimplemented with any programming or scripting language such as C, C++,C#, Java, COBOL, assembler, PERL, Python, PHP, or the like, with thevarious algorithms being implemented with any combination of datastructures, objects, processes, routines or other programming elements.The object code created may be executed by any device, on a variety ofoperating systems, including without limitation RTOS, Apple OSX®, AppleiOS®, Google Android®, HP WebOS®, Linux, UNIX®, Microsoft Windows®,and/or Microsoft Windows Mobile®.

It should be appreciated that the particular implementations describedherein are illustrative of the disclosure and its best mode and are notintended to otherwise limit the scope of the present disclosure in anyway. Examples are presented herein which may include data items whichare intended as examples and are not to be construed as limiting.Indeed, for the sake of brevity, conventional data networking,application development and other functional aspects of the systems (andcomponents of the individual operating components of the systems) maynot be described in detail herein. It should be noted that manyalternative or additional functional relationships or physical orvirtual connections may be present in a practical electronic system orapparatus. In the discussion contained herein, the terms user interfaceelement and/or button are understood to be non-limiting, and includeother user interface elements such as, without limitation, pushbutton, aproximity sensor, a hyperlink, clickable image, and the like.

As will be appreciated by one of ordinary skill in the art, the presentdisclosure may be embodied as a method, a data processing system, adevice for data processing, and/or a computer program product. Thepresent disclosure may take the form of a computer program product on acomputer-readable storage medium having computer-readable program codemeans embodied in the storage medium. Any suitable computer-readablestorage medium may be utilized, including hard disks, CD-ROM, DVD-ROM,optical storage devices, magnetic storage devices, semiconductor storagedevices (e.g., EEPROM, mask ROM, flash memory, USB thumb drives) and/orthe like.

Computer program instructions embodying the present disclosure may alsobe stored in a computer-readable memory that can direct a computer orother programmable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture, including instruction means,that implement the function specified in the description or flowchartblock(s). The computer program instructions may also be loaded onto acomputer or other programmable data processing apparatus to cause aseries of operational steps to be performed on the computer or otherprogrammable apparatus to produce a computer-implemented process suchthat the instructions that execute on the computer or other programmableapparatus provide steps for implementing the functions specified in thepresent disclosure.

One skilled in the art will also appreciate that, for security reasons,any components, data structures, and communications links may includeany of various suitable security features, such as firewalls, accesscodes, encryption, de-encryption, compression, decompression, and/or thelike. In some instances, the steps recited herein may be executed in anyorder and are not limited to the order presented.

Exemplary embodiments are disclosed herein which operate in accordancewith the ZigBee® wireless mesh networking standards, however, it shouldbe understood that embodiments of the present disclosure are applicableto any wired or wireless network architecture, including withoutlimitation Z-Wave®, in which the features and advantages discussedherein may be advantageously employed.

Referring to FIG. 1 , a wireless HVAC device 1 in accordance with thepresent disclosure is shown. Wireless HVAC device 1 includes a battery 4or other power source configured to provide operating power to amicrocontroller 6, a network interface 7, one or more input devices 5,and/or a display 8. Microcontroller 6 may include a processor, and amemory operatively associated with the processor, the memory storingexecutable instructions, which, when executed on the processor, performone or more of the methods described herein. Wireless HVAC device 1includes a sleep current fault detector 3 which detects excessivecurrent draw from battery 4 when HVAC device 1 is in a low-power, or“sleep” mode. Sleep current fault detector 3 includes sleep currentfault detection circuit 10, discussed in detail below.

Display 8 may include, without limitation, an LCD display, an electronicpaper display (e-paper) or any other suitable display which meets thelow-power and environmental requirements for an HVAC sensor. Display 8may be externally viewable during normal use, or may be concealed fromview during normal use but visible during an initial setup task, asdescribed below. Input device(s) 5 may include one or switches,pushbuttons, touchscreen, proximity sensor, or other input device. HVACdevice 1 includes a sensor 9, such as, without limitation, a temperaturesensor, a humidity sensor, a barometric pressure sensor, a light sensor,a proximity sensor, and the like.

Network interface 7 may include a radiofrequency (RF) transceiver thatis configured to facilitate communications in accordance with the802.15.4 standard. In embodiments, network interface 7 operates inaccordance with the ZigBee® wireless communications protocol.

With reference to FIG. 2 , a sleep current fault detection circuit 10 isdisclosed. Circuit 10 is adapted to work with a device 11, which mayinclude a microcontroller, radio module, or any other integrated ordiscrete circuit, which is operable in a normal, “awake” or “active”mode, and a low-power or “sleep” mode. Sleep current fault detectioncircuit 10 is suitable for battery-powered devices that spend asignificant amount of time in a low-powered (e.g., sleep) mode. Whilesuch a device is sleeping, if a fault occurs and current draw increases,battery life can be dramatically shortened. The disclosed sleep currentfault detection circuit 10 is designed to detect such failures, withnegligible energy consumption.

With continued reference to FIG. 2 , a positive terminal of battery 12is coupled to Vcc. A MOSFET 13 (Q2) is coupled in series between anegative terminal of battery 13 and ground 26. MOSFET 13 is configuredsuch that the body diode of MOSFET 13 is in a forward conducting statewhen device 11 is powered up e.g., the drain terminal of MOSFET 13 iscoupled to the negative terminal of battery 12, and the source terminalof MOSFET 13 is coupled to ground 26. Note that, because of the voltagedrop across the drain and source of MOSFET 13, the negative terminal ofbattery 12 will be at a lower potential than ground 26. Ground terminal24 of device 11 is also connected to ground 26.

In operation, before entering sleep mode, MOSFET 13 is turned off viaGPIO output 25. When device 11 awakes from sleep, MOSFET 13 is turned onvia GPIO output 25. During sleep mode, if the current consumed by device11 increases, so too does the voltage drop across the drain and sourceof MOSFET 13. During sleep mode with MOSFET 13 off, this voltage drop isabout 0.3V. If device 11 increases current draw during sleep, thevoltage drop across MOSFET 13 will increase. Therefore, by detectingthis increase in voltage drop, the current draw of device 11 isdetermined. If the voltage drops exceeds a predetermined limit, e.g.,greater than approximately 0.5V, an interrupt is flagged to an interruptterminal 23 of device 11. Advantageously, device 11 includes thecapability to monitor the activity of interrupt terminal 23 while insleep mode, and execute a task (wake up, execute an interrupt handler,etc.) in response to the sleep fault condition. In a typical scenario,the current draw of device 11 may be about 2 uA during sleep. A sleepcurrent failure circuit in accordance with the present exampleembodiment will detect an increase in sleep current draw of one or moreorders of magnitude. So, for example, a sleep current circuit inaccordance with the present example embodiment will trigger at about a20 uA current draw. Other embodiments are contemplated which detect evensmaller changes of current flow. In embodiments, The disclosed sleepcurrent fault detection circuit 10 may be configured to detect sleepcurrent faults in other circuit elements in addition to, oralternatively to, device 11.

The emitter terminal of a transistor 14 (Q3) is coupled to the drain ofMOSFET 13. The base of transistor 14 is coupled to ground 26. Duringnormal sleep mode, the base-emitter voltage across resistor 15 (R20),corresponding to the voltage drop across MOSFET 13, is low, which causestransistor 14 to remain off. If, however, a sleep fault occurs whichresults in excessive current draw, transistor 14 will switch on.Transistor 16 (Q4) and transistor 18 (Q5) are configured as bufferedgain stages which drive an interrupt terminal 23 of device 11 when asleep power fault is detected. An R-C network 19 formed by resistor 20(R4) and capacitor 21 (C8) delays the turn-on time of transistor 18 toprevent false positives and other spurious or transient conditions fromtriggering the interrupt to device 11.

Device 11 monitors interrupt terminal 23 while in sleep mode. Whentransistor 18 turns on, interrupt terminal 23 is pulled low which causesdevice 11 to wake up and perform a desired task. For example, device 11can display an error code, transmit to a receiver that it has a sleepcurrent issue, power down sections of the sensor to isolate the problem,or perform any other task which may be appropriate in response to asleep current failure.

Turning to FIGS. 3A-3F, a prior art ZigBee® wireless mesh network 30 isshown. A typical ZigBee® network includes one router acting as thecoordinator 31, optionally one or more other routers 32 and optionallyone or more end nodes 33. The coordinator 31 and other router(s) 32includes the capability to act as an intermediary to relay data fromsource devices to destination devices. Both the coordinator 31 androuter(s) are maintained in a powered-up mode, that is, neithercoordinator 31 nor router 32 may go into sleep mode. The end node(s) 33may include functionality to perform a task (such as sensing a conditionor accepting a user input). An end node 33 communicates through acoordinator 31 or a router 32 and is called a child of that router,which is called the parent of that end node. A parent node communicatesdirectly with its child node(s) and relays messages between its childnode(s) and other nodes in the mesh network. An end node 33 may enter asleep mode, and, in practice, may be in sleep mode most of the time toconserve battery life. Additionally, end nodes 33 typically include arelatively modest amount of computing resources, and therefore aretypically less expensive to manufacture than a coordinator 31 or router32.

Prior art network 30 typically operates as follows: Assume end node 33is to send a message to destination node 32 c. A message is typicallyformed by one or more packets containing a destination addresscorresponding to the destination node, and the data to be sent to thedestination node. The message is sent from the end node 33 to the parentnode 32 a and may be relayed through one or more other router nodesuntil it reaches the destination. At each handoff, the receiving nodetransmits a low-level acknowledgement (e.g., a data link layer, or MACacknowledgement, etc.) to the sending node to confirm receipt. When themessage reaches the destination node, the destination node, ifrequested, sends a higher-level acknowledgement message, such as an APSacknowledgement (APS ack), back to the originating node. The APS ack maybe relayed to the originating node through the same series of nodes inreverse, or may take a different route.

The source of a message, such as end node 33, must determine thedestination address of the destination node. To determine thedestination address, a station tag ID which includes identifyinginformation relating to the destination node is used to determine thedestination address. The destination address itself is not typicallyused as the tag ID, because network addresses are randomly assigned andmay change in a ZigBee® network. Tags may include, for example, the MACaddress of a wireless node, a protocol address of a ZigBee® deviceimplementing the generic tunnel cluster, or some independent informationconfigured by a user through a user interface, such as the settings ofjumpers or rotary dial switches or via a touch screen, buttons, etc.

As seen in FIG. 3A, end node 33 wakes up to send a message containingdata to, for example, router 32 c. Before sending the message the firsttime to a destination, the address of the destination node must bedetermined by end node 33. End node 33 queries the network to obtain theaddress of the destination node. For example, the ZigBee® standardprovides for broadcast requests to discover a node having a specifiedMAC address, and the generic tunnel cluster provides broadcast requeststo match a protocol address to a node. An application can, in general,provide for discovery of the node matching any desired tag. End node 33then formats the message by combining the message data with the addressof the destination node (router 32 c) to form one or more messagepackets. The message is then transmitted to the parent node, which, inthe present example, is router 32 a. The receiving node (here, router 32a) will transmit a MAC acknowledgement to the transmitting node (here,end node 33) to confirm receipt of the transmitted packet at the datalink level. Router 32 a receives the message, examines the destinationaddress, determines that the destination address belongs to a node otherthan itself, and, as seen in FIG. 3B, forwards the message to the nextnode. If router 32 a does not have a stored route for reaching thedestination node, then router 32 must discover a route before forwardingthe message. In some instances, router 32 may discard the message, onlyforwarding messages that end node 33 sends in the future when router 32has a stored route to the destination. Continuing with the presentexample, the next node is coordinator 31. Coordinator 31 repeats theprocess, and as shown in FIG. 3C, forwards the message to thedestination node e.g., router 32 c. Upon receipt, the destination nodetransmits an application acknowledgement message (APS ack) to theoriginating end node 33 via the reverse path from the original messageas shown in FIGS. 3D, 3E, and 3F. A function of APS acks is to enhancereliability. Since any one relay has a probability of failing, based onthe wireless link quality, and the overall probability of failure todeliver the message to the destination is the probability that any onerelay fails, the ZigBee® application support layer can use APS acks todetermine when to repeat sending a message so that message delivery ismore reliable. Another function of APS acks is to facilitate thedetection of when a destination address changes, so that the source candetermine the new address for the destination.

Several drawbacks exist in such prior art networks. An end node usesbattery power to wake up repeatedly to poll its parent node as the endnode attempts to receive the APS ack for each message it sends. The timeand power required may include time and power used for route discoveryand repeated transmissions. Each router maintains a routing table tostore the next relay for each destination to which it can forwardpackets in the mesh network. Such routing tables are allocated a finiteamount of memory and therefore can hold only up to a certain number ofentries. In order to make room for new routes, stale entries which areolder and/or lesser-used are purged from the table. To avoid unnecessaryroute discovery processes, the tables must be large enough to containentries for addresses of data destinations and end devices (which aredestinations of APS acks). These requirements are costly in terms ofpower consumption and computing resource usage.

FIGS. 4A-4F illustrate an exemplary embodiment of an energy-efficientwireless mesh network 50 that significantly extends battery life byminimizing the amount of time the end node needs to be awake, and bydelegating responsibility for finding the destination address to therouter. Embodiments of the present disclosure eliminate the need forrepetitive wake/poll/sleep cycles to receive an applicationacknowledgement by allowing a message to be reliably dispatched from anend node using a single radio transmission, while maintaining networkreliability by sending the message with APS acks to the destination.

With reference to FIG. 4A, the network 50 includes a battery-powered endnode 51, router nodes 52, 53, and 54, and coordinator node 55. Thenetwork configuration shown in the FIGS. 4A-4F is exemplary, and it isto be understood that embodiments having other configurations, e.g.,different numbers and types of nodes, links, devices, and the like, arecontemplated within the scope of the present disclosure. Each node isassigned a logical node address. In the present embodiment, end node 51is assigned an address of A1, routers 52, 53, and 54 are assignedaddresses A2, A3, and A5, respectively, and coordinator 55 is assignedaddress A4. End node 51 is assigned a tag of TA, routers 52, 53, and 54are assigned tags TB, TC, and TE, respectively, and coordinator 55 isassigned tag TD. Routers 52, 53, and 54 include an address map 56, 57,58, respectively, and coordinator 55 includes address map 59. An addressmap comprises a source address map and a destination address map.

As illustrated in FIG. 4A, end node 51 initiates a message transmissionto the tag corresponding to router 54. End node 51, which is typicallyin sleep mode, wakes up, and transmits message 1 to its parent node,here router 52. Upon receipt of message 1, router 52 transmits a MACacknowledgement back to end node 51. The MAC acknowledgement signifiesto end node 51, at the data link layer, that message 1 has beensuccessfully dispatched. In response, end node 51 returns to sleep mode.Advantageously, end node 51 remains in sleep mode until its nextscheduled wake-up, that is, once the brief transmission/MACacknowledgement cycle is complete, no further expenditure of batteryenergy by end node 51 is required to effectuate the transmission ofmessage 1. Message 1 includes the tag TE of the destination node (here,router 54).

As illustrated in FIG. 4B, router 52 is now the recipient of message 1.Router 52 determines from the tag whether it is the destination for thedata. If the tag in message 1 matches the tag of router 52 (TB), thenrouter 52 accepts the data for its application. Since in this example,the tag in message 1 (TE) matches the tag of router 54 (TE), router 52will forward the data by sending message 2 with the same tag and data asmessage 1, and including the data source address of end node 51 (A1).Router 52 sends message 2 through the ZigBee network to the coordinator55, preferably using APS acks. If router 52 is not able to communicatewith the coordinator, such as when the coordinator is powered down, orif the network design does not give advantage to routing messages to andfrom the coordinator, then router 52 instead of the coordinator findsthe destination and sends message 3 to the destination as describedbelow. The network design in the exemplary embodiment uses many-to-onerouting toward the coordinator, and source routing along the same routesoutbound from the coordinator, so there is an advantage to sendingmessages to and from the coordinator, avoiding route discovery androuting table entries for routes between other routers.

In FIG. 4C, coordinator 55 is in receipt of message 2. Routers 52, 53,54, and 55 include source address maps 56, 57, 58, 59, respectively, inwhich message source addresses and corresponding data source addressesare stored. Any router that receives message 2 stores the message sourceaddress and data source address in its source address map. Sourceaddress maps facilitate the transmission of responses, if requested,from the destination back to the source without discovering a route. Thecoordinator determines the destination address and sends to it message3, which contains the same tag and data as message 1 with the datasource address of end node 51, preferably using APS acks. Routersinclude destination address maps in maps 56 et al. in which tags andcorresponding destination addresses are stored. Any router that needs tosend message 3 stores the tag and data destination address in itsdestination address map.

Message 3 has arrived at the destination node, router 54. If the tag inmessage 3 does not match the tag in router 54, then router 54 willhandle message 3 in the same manner as router 52 handled message 1, andthe sender of message 3 will detect when it receives a message 2 fromthe address stored in its destination address map that the map entry isno longer valid, whereupon it will determine the new destination addressand send a new message 3. Otherwise, the tag in message 3 will match thetag in the destination, here router 54, so router 54 processes themessage. For example, the destination node may act upon the message inaccordance with the application function to which the message isdirected, e.g., record a temperature, activate or deactivate a heatpump, and so forth will be understood by one skilled in the art. If aresponse was requested by the originating node, then as shown in FIG.4D, the response message 4 containing the data source tag ID and theresponse is transmitted to the source of message 3 or, if the datasource is a child of the destination, to the data source. When a routerthat has recently sent a message 3 receives a response message 4, itsends a response message 5 to the message source address correspondingto the data source address in its source address map or, if the datasource is a child of the router that sent message 3, to the data source.In this case, map 59 indicates the message source corresponding to tagT1 was address A2 (router 52), therefore coordinator 53 sends responsemessage 5 to that node (FIG. 4E).

The response arrives at router 52. Router 52 determines that it is theparent node to the data source, end node 51, so it sends the responsemessage to the data source. Since end node 51 is a device capable ofsleep mode, the parent caches the message sent to the child. When thechild wakes up, the child polls the parent, and receives pending cachedmessages from the parent (FIG. 4F).

Turning now to FIGS. 5A-5D, an HVAC sensor 90 assemblable in a firstconfiguration 100 having an exposed display, shown in FIGS. 5A and 5B,and second configuration 110 having a concealed display, shown in FIGS.5C and 5D, is described. Advantageously, the disclosed HVAC sensor 90utilizes a printed circuit board 102 which is utilized in bothconfigurations, which increases economies of scale, reduces developmentand testing costs, and simplifies inventory control. Printed circuitboard 102 includes a display side and a non-display side, and may bemounted within sensor 90 with the display side facing inward or outward,as described in detail below.

In the first, visible-display configuration 100 seen in FIGS. 5A and 5B,sensor 90 includes a housing 101 having front portion 106 generallysuited for facing a user, and a rear portion 107 generally suited forattaching to a mounting surface, such as a wall. Housing front portion106 includes a display opening 105 and one or more switch openings 119defined therein. In the second, concealed-display configuration 110shown in FIGS. 5C and 5D, sensor 90 includes a housing 111 having ahaving front portion 116 generally suited for facing a user, and a rearportion 117 generally suited for attaching to a mounting surface, suchas a wall or column. In embodiments, one or more of front portion 106,front portion 116, rear portion 107, rear portion 117 and/or printedcircuit board 102 may be included in an installation kit which enablesan installer to select on-site which configuration (visible display orhidden display) is appropriate for a particular installation location.In some embodiments, rear portion 107 may be substituted for rearportion 117, and therefore, only one of rear portion 107 or rear portion117 need be included in the installation kit.

Sensor 90 includes a reversible printed circuit board 102 having adisplay module 103 operatively mounted thereupon. In embodiments,display module 103 may include a liquid crystal display (LCD).Alternatively, an electronic paper display (e-paper) or any othersuitable display which meets the low-power and environmentalrequirements for an HVAC sensor may be utilized, as will be appreciatedby the skilled artisan. Printed circuit board 102 includes a switchassembly 104 operatively coupled thereto which enables a user tointeract with sensor 90, for example, to set a device identifier, tojoin a wireless mesh network, to activate the display, and so forth.Printed circuit board 102 includes one or more notches 108 defined alonga peripheral edge thereof that are dimensioned to effectuate snap-fitengagement with corresponding mounting tabs 118 provided by sensorhousing 101 and/or sensor housing 111. Printed circuit board 102includes a pair of battery contacts 109 which are configured tooperatively engage one or more batteries 114. As best seen in FIGS. 5Band 5D, housing 101 and 111 are configured to retain the one or morebatteries 114 on opposite sides for one another as required toaccommodate printed circuit board 102 in its exposed displayconfiguration 100 and in its concealed display configuration 110.

In use, an installer may use display module 103 and switch assembly 104to perform initial setup of sensor 90, e.g., to set a device address,join a wireless mesh network, and so forth. This is readily performed inthe exposed display configuration 100, since the display 103 and switchassembly 104 are openly accessible. With the concealed displayconfiguration 110, the installer may separate the two halves of housing111 to access the display 103 and/or switch assembly 104 concealedtherewithin. Once the initial setup is complete, the housing isreassembled by reattaching front portion 116 and rear portion 117, andthe sensor 90 may be placed into service. Sensor 90 may be anpower-efficient HVAC sensor which includes a sleep current faultdetector 3, a power-efficient method 200 of operating a wireless HVACdevice, and/or other power-saving features described herein.

Turning to FIGS. 6 and 7 , a power-efficient method 200 of operating awireless HVAC device 210 is shown. HVAC device 210 includes switchassembly 205, a display 206, and may incorporate wireless sensor, athermostat, and so forth. In embodiments, display 206 may include atouchscreen display. HVAC device 210 is adapted for wirelesscommunication with one or more wireless nodes 220, 230. As shown,wireless nodes 220 a, 220 b, 230 include, but are not limited to, aZigBee® routing node (e.g., a wireless communication interface or WCI)and/or a ZigBee® coordinator node.

HVAC device 210 is typically mounted upon a wall or other surface thatis easily accessible to a user. At most times, HVAC device 210 operatesin a low-power sleep mode, which prolongs battery life. In someembodiments, during sleep mode display 206 may display onlylocally-available data items, e.g., data which does not require anetwork transmission to obtain. In this manner, power is furtherconserved by preventing the network circuitry (e.g., the 802.15.4transceiver) from powering up during sleep mode. In some embodiments,HVAC device 210 will deactivate display 206 during sleep mode in orderto further conserve power. In embodiments where HVAC device 210 includesa sensor, HVAC device 210 may periodically “wake up” into an activemode, transmit the current sensor reading, then return to sleep mode.

HVAC device 210 includes the capability of presenting data on display206, for example, it may display the locally-sensed sensor value and/ordata obtained via wireless communication from another network node.Since HVAC device 210 is, during the bulk of its lifecycle, simplymounted upon a wall and not being viewed or interacted with by a user,HVAC device 210 remains in sleep mode until a display request isexpressly made by a user.

In more detail, a user initiates a data display request in step 241,whereupon a user interacts with HVAC device 210 by actuating apushbutton 205, which may be a single press, a double press, or asimilar gesture. In embodiments where display 206 is a touchscreendisplay, a user may tap or swipe the display to initiate the request.Additionally or alternatively, a user may enter a choice of which dataitems the user wishes to view. For example, a single, initial actuationmay cause HVAC device 210 to proceed to display a default or preselecteddata item (such as system temperature setpoint). Additional actuations,for example, which navigate through a series of user interfaceselections, menus, etc., may allow the user to select alternative dataitems, groups of items, and so forth. Upon user actuation, HVAC device210 wakes up and prepares a data request message.

In step 242, HVAC device 210 transmits the data request message to thedestination node, and reverts to sleep mode. The data request message isrelayed by the wireless network (e.g., routers 220 a, 200 b) to thedestination node 230. In step 243, the destination node 230 transmitsthe requested data to HVAC device 210. Router 220 a is most adjacentnode to HVAC device 210, and so it is router 220 a which has the last“hop” to HVAC device 210. Router 220 a attempts to relay the response toHVAC device 210. Since HVAC device 210 has previously reverted to sleepmode, and is likely still in sleep mode, router 220 a is temporarilyunable to transmit the response to HVAC device 210. Therefore, in step224, router 220 a caches the response and begins to await a pollingmessage from HVAC device 210.

In step 245 HVAC device 210 wakes up and transmits a polling message toits network neighbor, e.g., router 220 a. In response, in step 246router 220 a transmits the data message to HVAC device 210. In turn, instep 247 HVAC device 210 presents the requested data on display 206 fora predetermined time, for example, about 3-5 seconds, and in step 248,HVAC device 210 return to sleep mode. By seeking to keep HVAC device 210in sleep mode and avoiding network transmissions for as long aspossible, in a reliable manner, and without impacting the userexperience, the disclosed methods provide extended battery life inwireless HVAC devices.

ASPECTS

It is noted that any of aspects 1-3 and aspects 4-8 below can becombined with each other in any combination, and may combined with anyof aspects 9-15, any of aspects 16-24, and/or any of aspects 25-26. Anyof aspects 9-15, any of aspects 16-24, and/or any of aspects 25-26 canbe combined with each other in any combination.

Aspect 1. A method of sensing excessive sleep current draw in abattery-powered device having a microcontroller, the method comprising:measuring a voltage drop across a MOSFET device coupled in aforward-conducting orientation in series between the battery and themicrocontroller; causing a transistor to conduct when the voltage dropexceeds a predetermined threshold to generate a first trigger signal;integrating the first trigger signal to generate a second triggersignal; and generating an interrupt to the microcontroller in responseto the second trigger signal.

Aspect 2. The method in accordance with aspect 1, wherein thepredetermined threshold is consistent with excessive current draw duringsleep.

Aspect 3. The method in accordance with any of aspects 1-2, furthercomprising transmitting, from the microcontroller, a fault signal inresponse to the interrupt.

Aspect 4. A sleep current fault detection circuit for use with a powereddevice operable in a sleep mode and an awake mode; comprising: a MOSFET,the drain terminal thereof coupled to a current source, the gateterminal thereof coupled to a powered device, the source terminalthereof coupled to ground; a first transistor, the emitter terminalthereof coupled to the drain terminal of the MOSFET and configured toconduct when the voltage across the drain terminal of the MOSFET and thesource terminal of the MOSFET exceeds a predetermined voltage; a secondtransistor, the base terminal thereof coupled to the collector of thefirst transistor, the collector terminal thereof coupled to an R-Cfilter; and a third transistor, the base terminal thereof coupled to theR-C filter, the collector terminal thereof coupled to an interruptterminal of the powered device.

Aspect 5. The circuit in accordance with aspect 4, wherein the gateterminal of the MOSFET is coupled to an output of the powered device.

Aspect 6. The circuit in accordance with any of aspects 4-5, wherein theoutput of the powered device turns off the MOSFET prior to enteringsleep mode.

Aspect 7. The circuit in accordance with any of aspects 4-6, wherein theoutput of the powered device turns on the MOSFET when entering awakemode.

Aspect 8. The circuit in accordance with any of aspects 4-7, wherein thepredetermined voltage is about 0.5 volts.

Aspect 9. In a mesh network having an end node operable in a sleep modeand an awake mode, an energy-efficient method of transmitting data fromthe end node to a destination node, comprising: transmitting a firstmessage, the first message including a tag ID of the destination nodeand message data, from the end node to a parent node of the end node;receiving, at the end node, a first acknowledgement from the parent nodeacknowledging receipt of the first message by the parent node; causingthe end node to enter sleep mode in response to the acknowledgement;determining, at the parent node, whether the parent node is thedestination node; and transmitting a second message, the second messageincluding the destination node tag, the message data, and a networkaddress of the parent node, to the destination node in response todetermination that the parent node is not the destination node.

Aspect 10. The method in accordance with aspect 9, further comprisingstoring, at the parent node, a relationship between the tag ID of theend node and a network address of the node from which the interveningnode received the second message.

Aspect 11. The method in accordance with any of aspects 9-10, whereintransmitting a second message including data from the first message fromthe parent node to the destination node includes relaying the secondmessage through an intervening node.

Aspect 12. The method in accordance with any of aspects 9-11, furthercomprising: storing, at the intervening node, a relationship between thetag ID of the end node and a network address of the node from which theintervening node received the second message.

Aspect 13. The method in accordance with any of aspects 9-12, furthercomprising: receiving, at the parent node, a second acknowledgement fromthe destination node; caching the second acknowledgement at the parentnode; receiving, from the end node, a poll request; and transmitting thesecond acknowledgement to the end node in response to the poll request.

Aspect 14. The method in accordance with any of aspects 9-13, whereinthe second acknowledgement includes an application layeracknowledgement.

Aspect 15. The method in accordance with any of aspects 9-14, whereinthe first acknowledgement includes a data link layer acknowledgement.

Aspect 16. A method of extending battery life in a wireless HVACcomponent operable in a sleep mode having a first power consumption andin an awake mode having a greater power consumption than when thecomponent is in the first mode, the method comprising: operating theHVAC component in the sleep mode; receiving, at a user interface elementof the HVAC component, a user input; operating the HVAC component in theawake mode; transmitting, from the HVAC component, a data requestmessage, wherein the data request message includes a device identifierof the destination device from which the data is requested; returningthe HVAC component to the sleep mode; forwarding the data requestmessage to the destination device; transmitting, from the destinationdevice, a response to the data request message; returning the HVACcomponent to the awake mode; polling an adjacent network node by theHVAC component; receiving, at the HVAC component, the response to thedata request message; displaying, on the HVAC component, informationderived from the response and; returning the HVAC component to the sleepmode.

Aspect 17. The method in accordance with aspect 16, further comprisingcaching, at an adjacent network node, the response to the data requestmessage.

Aspect 18. The method in accordance with any of aspects 16-17, whereinthe user interface element is selected from the group consisting of apushbutton and a proximity sensor.

Aspect 19. The method in accordance with any of aspects 16-18, whereinthe forwarding includes relaying the data request message through one ormore intervening devices.

Aspect 20. The method in accordance with any of aspects 16-19, whereinthe data request message includes a data item selected from the groupconsisting of a set point, a mode indicator, a temperature indicator, anHVAC system status, a fuel indicator, an energy indicator, a batterylevel indicator, and a signal strength indicator.

Aspect 21. The method in accordance with any of aspects 16-20, whereinthe mode indicator is selected from the group consisting of a coolingmode indicator, a heating mode indicator, a fan mode indicator, aventilation mode indicator, and a service mode indicator.

Aspect 22. The method in accordance with any of aspects 16-21, whereinthe temperature indicator is selected from the group consisting of anindoor temperature, an outdoor temperature, a refrigerant temperature,an HVAC equipment inlet temperature, and an HVAC equipment outlettemperature.

Aspect 23. The method in accordance with any of aspects 16-22, whereinthe fuel indicator is selected from the group consisting of a fuel flowrate indicator, a fuel level indicator, and a fuel pressure indicator.

Aspect 24. The method in accordance with any of aspects 16-23, whereinthe energy indicator is selected from the group consisting of a voltageindicator, a current indicator, and an alternating current frequencyindicator, a utility energy source indicator and a backup energy sourceindicator.

Aspect 25. A kit for manufacturing an HVAC sensor assemblable in a firstconfiguration having an exposed display and second configuration havinga hidden display, the kit comprising: a printed circuit board having adisplay side and a non-display side, the display side including adisplay module disposed thereon; a first housing assembly having a usersurface and a mounting surface; the user surface having a displayopening defined therein; the first housing assembly configured tooperatively receive the printed circuit board whereby the display modulefaces the user surface and is visible through the display opening; and asecond housing assembly having a user surface and a mounting surface andconfigured to operatively receive the printed circuit board whereby thedisplay module faces an interior surface of the housing.

Aspect 26. The kit in accordance with aspect 25, wherein: the printedcircuit board further comprises a switch assembly disposed on thedisplay side thereof, the first housing assembly further comprises aswitch assembly opening defined in the user surface thereof, the switchassembly opening configured to operably receive the switch assembly.

Particular embodiments of the present disclosure have been describedherein, however, it is to be understood that the disclosed embodimentsare merely examples of the disclosure, which may be embodied in variousforms. Well-known functions or constructions are not described in detailto avoid obscuring the present disclosure in unnecessary detail.Therefore, specific structural and functional details disclosed hereinare not to be interpreted as limiting, but merely as a basis for theclaims and as a representative basis for teaching one skilled in the artto variously employ the present disclosure in any appropriately detailedstructure.

What is claimed is:
 1. An apparatus comprising: a battery comprisingpositive and negative terminals; an integrated circuit (IC); a faultdetection circuit coupled to the battery and controlled by the IC, thefault detection circuit comprising: a metal oxide field effecttransistor (MOSFET) comprising a drain coupled to the negative terminal,a source coupled to a ground node, and a gate controlled by the IC;wherein the fault detection circuit, when activated by the IC, isconfigured to monitor a voltage between the source and drain; whereinthe fault detection circuit is configured to assert a signal if thevoltage exceeds a predetermined value; wherein the IC activates thefault detection circuit by deactivating the MOSFET.
 2. The apparatus ofclaim 1, wherein the fault detection circuit, when deactivated by theIC, does not monitor the voltage between the source and drain.
 3. Theapparatus of claim 1, further comprising a plurality of devices that arecoupled to and configured to receive direct current (DC) power from thebattery.
 4. The apparatus of claim 1, wherein the IC is configured toreceive the signal from the fault detection circuit.
 5. The apparatus ofclaim 4, wherein the IC is configured to operate in active mode or lowpower sleep mode, and wherein the IC is configured to switch from thelow power sleep mode to the active mode when the signal it receives isasserted.
 6. The apparatus of claim 5, further comprising: a displaydevice coupled to the IC; wherein the IC is configured to generate anerror code for display on the display device in response to switchingfrom the low power mode to the active mode.
 7. The apparatus of claim 1,wherein the fault detection circuit further comprises a transistorcoupled to the negative terminal of the battery and configured toconduct current when the voltage between the source and drain exceedsthe value.
 8. The apparatus of claim 7, wherein the fault detectioncircuit further comprises a buffered gain stage coupled to thetransistor and configured to assert the signal when the transistorconducts current.
 9. An apparatus comprising: a printed circuit board(PCB); a battery mounted on the PCB, wherein the battery comprisespositive and negative terminals; a plurality of devices, including adisplay device and wireless communication device, mounted on the PCB andcoupled to receive direct current (DC) power from the battery; a currentmonitor mounted on the PCB and coupled to the battery, wherein thecurrent monitor comprises a metal oxide field effect transistor (MOSFET)connected between the negative terminal and a ground node, and whereinthe current monitor is configured to operate in an active mode when theMOSFET is deactivated or an inactive mode when the MOSFET is activated;wherein the current monitor, when operating in the active mode, isconfigured to generate an error code for display on the display deviceif the current exceeds a predetermined value.